Added byte-level UART implementation.
Remove (unused) buffering feature from RX.
Add untested high-level UART packet interface block.
Varified UART design.
Added UART to raggedstone_ftdi design.
Add constraints for FTDI interface.
Merge branch 'master' into old_rxc_txc
Added UART to raggedstone requirements.
Fixed baudrate counter.
Merge branch 'master' into old_rxc_txc
Add tempoary link blocking fix.
Merge branch 'master' into old_rxc_txc